Biopolar electrosurgical instruments apply radiofrequency (RF) energy to a surgical site to cut, ablate, or coagulate tissue. A particular application of these electrosurgical effects is to seal blood vessels or tissue sheets. A typical instrument takes the form of a set of forceps or pair of jaws, with one or more electrodes on each jaw tip. In an electrosurgical procedure, the electrodes are placed in close proximity to each other as the jaws are closed on a target site such that the path of alternating current between the two electrodes passes through tissue within the target site. The mechanical force exerted by the jaws and the electrical current combine to create the desired surgical effect. By controlling the level of mechanical and electrical parameters, such as the pressure applied by the jaws, the gap distance between electrodes, and the voltage, current, frequency, and duration of the electrosurgical energy applied to the tissue, the surgeon can coagulate, cauterize, or seal tissue toward a therapeutic end.
Electrosurgical procedures can be performed in an open environment, through conventional incisions, or they may be performed laparoscopically, through small incisions, typically 0.5 cm-1.5 cm in length. A laparoscopic procedure may include the use of a telescopic rod lens system that is connected to a video camera and to a fiber optic cable system that conveys light to illuminate the operative field. A laparoscope is typically inserted into a port in the body through a 5 mm or 10 mm cannula or trocar to view the operative field. Surgery is performed during a laparoscopic procedure with any of various tools that are typically arranged at the distal end of a shaft and are operable by manipulation of a handle or an actuator positioned at the proximal end of the shaft, and are dimensioned such that they can pass through a port provided by the 5 mm or 10 mm cannula.
As electrosurgical tools are applied in laparoscopic procedures, challenges to the devices arise regarding dimensional constraints imposed by the operating environment, including the smallness of a typical port of entry, which includes the use of conventional trocars with a 5 mm inner diameter. The technology provided herein addresses the need for improvements in device technology, that permit downsizing of the device while maintaining appropriate levels of mechanical strength and electrosurgical capability. For example, it is generally desirable to extend the length of conventional forceps in order to allow the sealing of greater lengths of tissue. As forceps length increases, it becomes a challenge to exert an appropriate level of force, particularly from the distal end of the forceps. The present disclosure provides technologies that represent progress in addressing these challenges.